Java Code Examples for java.util.Collections#emptyIterator()

/**
 * Returns an iterator over property values used in the {@code for each...in} statement. Aside from built-in JS
 * objects, it also operates on Java arrays, any {@link Iterable}, as well as on {@link Map} objects, iterating over
 * map values.
 * @param obj object to iterate on.
 * @return iterator over the object's property values.
 */
public static Iterator<?> toValueIterator(final Object obj) {
    if (obj instanceof ScriptObject) {
        return ((ScriptObject)obj).valueIterator();
    }

    if (obj instanceof JSObject) {
        return ((JSObject)obj).values().iterator();
    }

    final Iterator<?> itr = iteratorForJavaArrayOrList(obj);
    if (itr != null) {
        return itr;
    }

    if (obj instanceof Map) {
        return ((Map<?,?>)obj).values().iterator();
    }

    final Object wrapped = Global.instance().wrapAsObject(obj);
    if (wrapped instanceof ScriptObject) {
        return ((ScriptObject)wrapped).valueIterator();
    }

    return Collections.emptyIterator();
}
 

@Override
public Iterator<R> call(Iterator<MultiDataSet> dataSetIterator) throws Exception {
    //Under some limited circumstances, we might have an empty partition. In this case, we should return immediately
    if(!dataSetIterator.hasNext()){
        return Collections.emptyIterator();
    }
    /*
        That's the place where we do our stuff. Here's the plan:
        1) we pass given iterator to VirtualDataSetIterator, which acts as holder for them
        2) Virtual iterator will provide load balancing between available devices
        3) we'll lock out here
     */

    // iterator should be silently attached to VirtualDataSetIterator, and used appropriately
    SharedTrainingWrapper.getInstance(worker.getInstanceId()).attachMDS(dataSetIterator);

    // first callee will become master, others will obey and die
    // all threads in this executor will be blocked here until training finished
    SharedTrainingResult result = SharedTrainingWrapper.getInstance(worker.getInstanceId()).run(worker);

    return Collections.singletonList((R) result).iterator();
}
 

/**
 * Returns an <code>Iterator</code> containing all currently
 * registered <code>ImageTranscoder</code>s that claim to be
 * able to transcode between the metadata of the given
 * <code>ImageReader</code> and <code>ImageWriter</code>.
 *
 * @param reader an <code>ImageReader</code>.
 * @param writer an <code>ImageWriter</code>.
 *
 * @return an <code>Iterator</code> containing
 * <code>ImageTranscoder</code>s.
 *
 * @exception IllegalArgumentException if <code>reader</code> or
 * <code>writer</code> is <code>null</code>.
 */
public static Iterator<ImageTranscoder>
    getImageTranscoders(ImageReader reader, ImageWriter writer)
{
    if (reader == null) {
        throw new IllegalArgumentException("reader == null!");
    }
    if (writer == null) {
        throw new IllegalArgumentException("writer == null!");
    }
    ImageReaderSpi readerSpi = reader.getOriginatingProvider();
    ImageWriterSpi writerSpi = writer.getOriginatingProvider();
    ServiceRegistry.Filter filter =
        new TranscoderFilter(readerSpi, writerSpi);

    Iterator iter;
    // Ensure category is present
    try {
        iter = theRegistry.getServiceProviders(ImageTranscoderSpi.class,
                                        filter, true);
    } catch (IllegalArgumentException e) {
        return Collections.emptyIterator();
    }
    return new ImageTranscoderIterator(iter);
}
 

/**
 * Returns an <code>Iterator</code> containing all currently
 * registered <code>ImageWriter</code>s that claim to be able to
 * encode the named format.
 *
 * @param formatName a <code>String</code> containing the informal
 * name of a format (<i>e.g.</i>, "jpeg" or "tiff".
 *
 * @return an <code>Iterator</code> containing
 * <code>ImageWriter</code>s.
 *
 * @exception IllegalArgumentException if <code>formatName</code> is
 * <code>null</code>.
 *
 * @see javax.imageio.spi.ImageWriterSpi#getFormatNames
 */
public static Iterator<ImageWriter>
    getImageWritersByFormatName(String formatName)
{
    if (formatName == null) {
        throw new IllegalArgumentException("formatName == null!");
    }
    Iterator iter;
    // Ensure category is present
    try {
        iter = theRegistry.getServiceProviders(ImageWriterSpi.class,
                                new ContainsFilter(writerFormatNamesMethod,
                                                   formatName),
                                        true);
    } catch (IllegalArgumentException e) {
        return Collections.emptyIterator();
    }
    return new ImageWriterIterator(iter);
}
 

@Override
protected Iterator<E> flatMap(Traverser.Admin<Element> traverser) {
    if (useMultiQuery) { //it is guaranteed that all elements are vertices
        if (multiQueryResults == null || !multiQueryResults.containsKey(traverser.get())) {
            initializeMultiQuery(Arrays.asList(traverser));
        }
        return convertIterator(multiQueryResults.get(traverser.get()));
    } else if (traverser.get() instanceof JanusGraphVertex || traverser.get() instanceof WrappedVertex) {
        JanusGraphVertexQuery query = makeQuery((JanusGraphTraversalUtil.getJanusGraphVertex(traverser)).query());
        return convertIterator(query.properties());
    } else {
        //It is some other element (edge or vertex property)
        Iterator<E> iterator;
        if (getReturnType().forValues()) {
            iterator = traverser.get().values(getPropertyKeys());
        } else {
            //HasContainers don't apply => empty result set
            if (!hasContainers.isEmpty()) return Collections.emptyIterator();
            iterator = (Iterator<E>) traverser.get().properties(getPropertyKeys());
        }
        if (limit != Query.NO_LIMIT) iterator = Iterators.limit(iterator, limit);
        return iterator;
    }
}
 

/**
 * Returns an <code>Iterator</code> containing all currently
 * registered <code>ImageWriter</code>s that claim to be able to
 * encode files with the given suffix.
 *
 * @param fileSuffix a <code>String</code> containing a file
 * suffix (<i>e.g.</i>, "jpg" or "tiff").
 *
 * @return an <code>Iterator</code> containing <code>ImageWriter</code>s.
 *
 * @exception IllegalArgumentException if <code>fileSuffix</code> is
 * <code>null</code>.
 *
 * @see javax.imageio.spi.ImageWriterSpi#getFileSuffixes
 */
public static Iterator<ImageWriter>
    getImageWritersBySuffix(String fileSuffix)
{
    if (fileSuffix == null) {
        throw new IllegalArgumentException("fileSuffix == null!");
    }
    Iterator iter;
    // Ensure category is present
    try {
        iter = theRegistry.getServiceProviders(ImageWriterSpi.class,
                               new ContainsFilter(writerFileSuffixesMethod,
                                                  fileSuffix),
                                        true);
    } catch (IllegalArgumentException e) {
        return Collections.emptyIterator();
    }
    return new ImageWriterIterator(iter);
}
 

/**
 * Returns an <code>Iterator</code> containing all currently
 * registered <code>ImageWriter</code>s that claim to be able to
 * encode the named format.
 *
 * @param formatName a <code>String</code> containing the informal
 * name of a format (<i>e.g.</i>, "jpeg" or "tiff".
 *
 * @return an <code>Iterator</code> containing
 * <code>ImageWriter</code>s.
 *
 * @exception IllegalArgumentException if <code>formatName</code> is
 * <code>null</code>.
 *
 * @see javax.imageio.spi.ImageWriterSpi#getFormatNames
 */
public static Iterator<ImageWriter>
    getImageWritersByFormatName(String formatName)
{
    if (formatName == null) {
        throw new IllegalArgumentException("formatName == null!");
    }
    Iterator iter;
    // Ensure category is present
    try {
        iter = theRegistry.getServiceProviders(ImageWriterSpi.class,
                                new ContainsFilter(writerFormatNamesMethod,
                                                   formatName),
                                        true);
    } catch (IllegalArgumentException e) {
        return Collections.emptyIterator();
    }
    return new ImageWriterIterator(iter);
}
 

/**
 * Returns an <code>Iterator</code> containing all currently
 * registered <code>ImageWriter</code>s that claim to be able to
 * encode the named format.
 *
 * @param formatName a <code>String</code> containing the informal
 * name of a format (<i>e.g.</i>, "jpeg" or "tiff".
 *
 * @return an <code>Iterator</code> containing
 * <code>ImageWriter</code>s.
 *
 * @exception IllegalArgumentException if <code>formatName</code> is
 * <code>null</code>.
 *
 * @see javax.imageio.spi.ImageWriterSpi#getFormatNames
 */
public static Iterator<ImageWriter>
    getImageWritersByFormatName(String formatName)
{
    if (formatName == null) {
        throw new IllegalArgumentException("formatName == null!");
    }
    Iterator iter;
    // Ensure category is present
    try {
        iter = theRegistry.getServiceProviders(ImageWriterSpi.class,
                                new ContainsFilter(writerFormatNamesMethod,
                                                   formatName),
                                        true);
    } catch (IllegalArgumentException e) {
        return Collections.emptyIterator();
    }
    return new ImageWriterIterator(iter);
}
 

/**
 * Returns an {@code Iterator} containing all currently
 * registered {@code ImageTranscoder}s that claim to be
 * able to transcode between the metadata of the given
 * {@code ImageReader} and {@code ImageWriter}.
 *
 * @param reader an {@code ImageReader}.
 * @param writer an {@code ImageWriter}.
 *
 * @return an {@code Iterator} containing
 * {@code ImageTranscoder}s.
 *
 * @exception IllegalArgumentException if {@code reader} or
 * {@code writer} is {@code null}.
 */
public static Iterator<ImageTranscoder>
    getImageTranscoders(ImageReader reader, ImageWriter writer)
{
    if (reader == null) {
        throw new IllegalArgumentException("reader == null!");
    }
    if (writer == null) {
        throw new IllegalArgumentException("writer == null!");
    }
    ImageReaderSpi readerSpi = reader.getOriginatingProvider();
    ImageWriterSpi writerSpi = writer.getOriginatingProvider();
    ServiceRegistry.Filter filter =
        new TranscoderFilter(readerSpi, writerSpi);

    Iterator<ImageTranscoderSpi> iter;
    // Ensure category is present
    try {
        iter = theRegistry.getServiceProviders(ImageTranscoderSpi.class,
                                        filter, true);
    } catch (IllegalArgumentException e) {
        return Collections.emptyIterator();
    }
    return new ImageTranscoderIterator(iter);
}
 

@Override
public Iterator<Map.Entry<String, V>> getRange(int skip, int take) {
  try {
    // list only files with sys file suffix
    PathFilter sysFileSuffixFilter = new PathFilter() {
      @Override
      public boolean accept(Path path) {
        return path.getName().endsWith(DRILL_SYS_FILE_SUFFIX);
      }
    };

    List<FileStatus> fileStatuses = DrillFileSystemUtil.listFiles(fs, basePath, false, sysFileSuffixFilter);
    if (fileStatuses.isEmpty()) {
      return Collections.emptyIterator();
    }

    List<String> files = Lists.newArrayList();
    for (FileStatus stat : fileStatuses) {
      String s = stat.getPath().getName();
      files.add(s.substring(0, s.length() - DRILL_SYS_FILE_SUFFIX.length()));
    }

    Collections.sort(files);

    return Iterables.transform(Iterables.limit(Iterables.skip(files, skip), take), new Function<String, Entry<String, V>>() {
      @Nullable
      @Override
      public Entry<String, V> apply(String key) {
        return new ImmutableEntry<>(key, get(key));
      }
    }).iterator();
  } catch (IOException e) {
    throw new RuntimeException(e);
  }
}
 

static Iterator<RecordReader> createReaders(
    final HiveConf hiveConf,
    final BaseHiveStoragePlugin hiveStoragePlugin,
    final FragmentExecutionContext fragmentExecContext,
    final OperatorContext context,
    final HiveProxyingSubScan config,
    final HiveTableXattr tableXattr,
    final CompositeReaderConfig compositeReader,
    final UserGroupInformation readerUGI,
    List<SplitAndPartitionInfo> splits) {

  try (ContextClassLoaderSwapper ccls = ContextClassLoaderSwapper.newInstance()) {

    if(splits.isEmpty()) {
      return Collections.emptyIterator();
    }

    final JobConf jobConf = new JobConf(hiveConf);

    final List<HiveParquetSplit> sortedSplits = Lists.newArrayList();
    for (SplitAndPartitionInfo split : splits) {
      sortedSplits.add(new HiveParquetSplit(split));
    }
    Collections.sort(sortedSplits);

    return new HiveParquetSplitReaderIterator(
            jobConf,
            context,
            config,
            sortedSplits,
            readerUGI,
            compositeReader,
            hiveStoragePlugin,
            tableXattr);
  } catch (final Exception e) {
    throw Throwables.propagate(e);
  }
}
 

@Override
public Iterator<ExecRow> fetchInner(ExecRow outer) throws IOException, StandardException{

    for (int i = 0; i < numKeys; i++) {
        keyRow.setColumn(i+1, outer.getColumn(outerHashKeys[i] + 1));
    }
    
    List<ExecRow> rows = table.get(keyRow);
    if(rows==null)
        return Collections.emptyIterator();
    else
        return rows.iterator();
}
 

@Override
public Iterator<Extension> iterator() {
    if (matches) {
        return extensions.iterator();
    }
    return Collections.emptyIterator();
}
 

static <E> CloseableIterable<E> empty() {
  return new CloseableIterable<E>() {
    @Override
    public void close() {
    }

    @Override
    public Iterator<E> iterator() {
      return Collections.emptyIterator();
    }
  };
}
 

private TaskSlotIterator(JobID jobId, TaskSlotState state) {

			Set<AllocationID> allocationIds = slotsPerJob.get(jobId);

			if (allocationIds == null || allocationIds.isEmpty()) {
				allSlots = Collections.emptyIterator();
			} else {
				allSlots = allocationIds.iterator();
			}

			this.state = Preconditions.checkNotNull(state);

			this.currentSlot = null;
		}
 

/**
 * Returns an iterator over property values used in the {@code for each...in} statement. Aside from built-in JS
 * objects, it also operates on Java arrays, any {@link Iterable}, as well as on {@link Map} objects, iterating over
 * map values.
 * @param obj object to iterate on.
 * @return iterator over the object's property values.
 */
public static Iterator<?> toValueIterator(final Object obj) {
    if (obj instanceof ScriptObject) {
        return ((ScriptObject)obj).valueIterator();
    }

    if (obj != null && obj.getClass().isArray()) {
        final Object array  = obj;
        final int    length = Array.getLength(obj);

        return new Iterator<Object>() {
            private int index = 0;

            @Override
            public boolean hasNext() {
                return index < length;
            }

            @Override
            public Object next() {
                if (index >= length) {
                    throw new NoSuchElementException();
                }
                return Array.get(array, index++);
            }

            @Override
            public void remove() {
                throw new UnsupportedOperationException("remove");
            }
        };
    }

    if (obj instanceof JSObject) {
        return ((JSObject)obj).values().iterator();
    }

    if (obj instanceof Map) {
        return ((Map<?,?>)obj).values().iterator();
    }

    if (obj instanceof Iterable) {
        return ((Iterable<?>)obj).iterator();
    }

    final Object wrapped = Global.instance().wrapAsObject(obj);
    if (wrapped instanceof ScriptObject) {
        return ((ScriptObject)wrapped).valueIterator();
    }

    return Collections.emptyIterator();
}
 

@Override
public Iterator<Edge> edges(final Object... edgeIds) {
    return Collections.emptyIterator();
}
 

@Override
public Iterator<LogicalExpression> iterator() {
  return Collections.emptyIterator();
}
 

@Override
public Iterator<DataCell> iterator(){
    if(result==null||result.isEmpty()) return Collections.emptyIterator();
    return Iterators.transform(result.listCells().iterator(),transform);
}
 

@Override public Iterator<T> iterator() { return Collections.emptyIterator(); }